Preheat your oven to 110°C/225°F. In a mixing bowl, whisk egg whites with cream of tartar until soft peaks form. Gradually add caster sugar, whisking until you achieve stiff peaks. Pipe the mixture into bone shapes on lined baking sheets and bake for 1.5 hours, until firm.

In a saucepan, combine frozen mixed berries, sugar, and water. Bring to a boil, then simmer until thickened, about 10-15 minutes. Cool the mixture before blending it until smooth; sieve to remove any seeds.

Preheat your oven to 180°C/350°F. In a bowl, mix cocoa powder with cold water, then add boiling water and chopped dark chocolate. In another bowl, beat butter with dark muscovado sugar and sweetened condensed milk until fluffy. Add in medium eggs and the flour mixture alternately. Pour into greased cake tins and bake for about 25 minutes, until a toothpick comes out clean.

In a heatproof bowl, whisk egg whites and sugar over simmering water until sugar dissolves (about 60°C/140°F). Once cooled, whisk until stiff peaks form, then gradually add butter, mixing until smooth. Finally, stir in vanilla extract and a pinch of salt.

Once the cake layers have cooled, level them off. Spread a layer of buttercream on one layer, add raspberry jam, and stack another layer on top. Spread buttercream around the sides and top of the cake. Decorate with meringue bones and drizzle the berry coulis on top for a spooky presentation.